Phylogenetic analysis of Dengue 4 based on the Envelope (E) gene sequence. The ML tree was constructed using the PhyML 3.0  software. Bootstrap values for 1000 replicates are indicated on each branch. The scale at the bottom indicates the number of nucleotide substitutions per site. The Indian strains are indicated in bold letters, HM indicates Hyderabad and the isolate sequenced in the present study is underlined.